Anthraquinone compound, liquid crystal composition, cell and display device employing the same

ABSTRACT

A liquid crystal composition comprising at least one liquid crystal compound and at least one anthraquinone compound represented by formula (1) below: Formula (1) (wherein R 2  to R 8  each independently represents a hydrogen or substituent; Het is a sulfur or oxygen; B 1  and B 2  each independently represents an optionally substituted arylene, heteroarylene, cycloalkan-diyl or cycloalken-diyl; Q 1  is a bivalent linking group; C 1  is an optionally substituted alkyl, cycloalkyl, alkoxy, alkokycarbonyl or acyloxy; p, q and r each represents a number from 0 to 5 and n is a number from 1 to 3 satisfying 3≦(p+r)×n≦10; when plural {(B 1 ) p -(Q 1 ) q -(B 2 ) r } are present, these may be the same or different) was disclosed

TECHNICAL FIELD

The present invention belongs to a technical field of novelanthraquinone compounds and liquid crystal compositions that maypreferably be used for liquid crystal displays, especiallyguest-host-type liquid crystal displays, and liquid crystal devicesemploying thereof.

BACKGROUND ART

There are known various types of liquid crystal devices For example,guest-host-type liquid crystal device has a cell having filled therein aliquid crystal composition which comprises liquid crystal as host anddichroic dye dissolved therein as guest. When a voltage is applied tothe cell sufficient to rotate the liquid crystal molecules, the dyemolecules rotate along with the liquid crystal molecules and allowchanging of light absorption by the cell to thereby effect display. Thereflective liquid crystal device employing guest-host mode is excellentin brightness.

Dichroic dyes used in liquid crystal devices are required to haveappropriate absorption characteristics, high order parameters, highsolubilities for host liquid crystal and excellent durabilities. Theorder parameter S is defined as “S=(3cos² θ−1)/2” when molecular longaxes of molecules, which receive thermal wobble, are learning atime-average angle lag “θ” from directors. “S” is 0.0 indicating thatmolecules are in absolute disordered state, on the other, “S” is 1.0indicating that molecules are in ordered state in which molecular longaxes and directors meet in alignment.

There are few known diachronic dyes which can bring about enough highorder parameter, and this result in a lowering of the contrast ofguest-host-type displays. Some azo and anthraquinone dyes are known asdichroic dyes bringing about relatively high order parameters. Forexample, some anthraquinone compounds are disclosed in JP-A-62-64886,JP-A-2-178390 and JP-A-10-260386 (the term “JP-A” as used herein meansan “unexamined published Japanese patent application”). However,solubilities of such dyes for host liquid crystal, especiallyfluorine-containing liquid crystal which has often been used in recentyears, are so low that liquid crystal displays employing such dyescannot have sufficient high optical densities.

It is therefore an object of the present invention to provide a liquidcrystal composition and a liquid crystal cell which can contribute toimprovement of displaying contrast and bring about high optical density,when employed in displaying devices. Another object of the presentinvention is to provide novel anthraquinone dyes which are useful asdichroic dyes, and in especial novel anthraquinone dyes bringing abouthigh order parameters and having high solubilities for host crystalliquid.

DISCLOSURE OF INVENTION

In one embodiment, this invention relates to a liquid crystalcomposition comprising liquid crystal compound and at least oneanthraquinone compound represented by formula (1) below:

(wherein R², R³, R⁴, R⁵, R⁶) R⁷ and R⁸ each independently represents ahydrogen or substituent; Het is a sulfur or oxygen; B¹ and B² eachindependently represents an optionally substituted arylene,heteroarylene, cycloalkan-diyl or cycloalken-diyl and when plural B¹ andB² are present, these may be the same or different; Q¹ is a bivalentlinking group and when plural Q¹ are present, these may be the same ordifferent; C¹ is an optionally substituted alkyl, cycloalkyl, alkoxy,alkokycarbonyl or acyloxy; p, q and r each represents a number from 0 to5 and n is a number from 1 to 3 satisfying 3≦(p+r)×n≦10; when plural{(B¹)_(p)-(Q¹)_(q)-(B²)_(r)} are present, these may be the same ordifferent).

As preferred embodiments of the present invention, there are providedthe liquid crystal composition wherein Het is a sulfur atom; the liquidcrystal composition wherein the anthraquinone compound is represented byformula (2) below:

(where S is a sulfur atom; A, B and C each independently represents anoptionally substituted arylene, heteroarylene or cyclohexandiyl; D is anoptionally substituted alkyl, cycloalkyl, alkoxy, alkoxycarbonyl oracyloxy; X¹, Y¹ and Z¹ each independently represents a hydrogen atom,halogen atom, hydroxyl, optionally substituted amino, arylthio orheteroarylthio, provided X¹, Y¹ and Z¹ are not all hydrogen; preferablyat least one of Z¹, X¹ and Y¹ represents an alkylamino); the liquidcrystal composition wherein the anthraquinone compound is represented byformula (3) below:

(where S, A, B, C and D are as defined above with respect to Formula(2), Z² represents an optionally substituted arylthio orheteroarylthio); the liquid crystal composition of Formula (1), whereinthe anthraquinone compound is represented by formula (4) below:

(where S, A, B, C and D are as defined above with respect to Formula(2), Z³ represents an optionally substituted arylthio orheteroarylthio); the liquid crystal composition wherein theanthraquinone compound is represented by formula (5) below:

(where S, A, B, C and D are as defined above with respect to Formula(2), Z⁴ and Z⁵ each independently represents an optionally substitutedarylthio or heteroarylthio); the liquid crystal composition of Formula(1), wherein the anthraquinone compound is represented by formula (6)below:

(where S, A, B, C and D are as defined above with respect to Formula(2), Z⁶ and Z⁷ each independently represents an optionally substitutedarylthio or heteroarylthio).

In another embodiment, this invention relates to a liquid crystal cellcomprising a liquid crystal layer containing a liquid crystalcomposition which comprises at least one liquid crystal compound and atleast one anthraquinone compound represented by said formula (1).

In another embodiment, this invention related to a display devicecomprising a liquid crystal cell comprising a liquid crystal layercontaining a liquid crystal composition which comprises at least oneliquid crystal compound and at least one anthraquinone compoundrepresented by said formula (1).

In another embodiment, this invention relates to an anthraquinonecompound represented by formula (1-a) below:

(where S is a sulfur atom; A, B and C each independently represents anoptionally substituted arylene, heteroarylene or cyclohexandiyl; Drepresents an optionally substituted alkyl, cycloalkyl, alkoxy,alkoxycarbonyl or acyloxy; X^(a), Y^(a) and Z^(a) each independentlyrepresents a hydrogen atom, optionally substituted amino, arylthio orheteroarylthio, provided at least one of X^(a), Y^(a) and Z^(a)represents an optionally substituted arylthio).

As preferred embodiments of the present invention, there are providedthe anthraquinone compound wherein X^(a) and Z^(a) are hydrogen, andY^(a) is an optionally substituted arylthio; the anthraquinone compoundwherein X^(a), Y^(a) and Z^(a) each independently represents anoptionally substituted arylthio; the anthraquinone compound whereinY^(a) and Z^(a) are each independently optionally substituted alkylaminoor arylamino, and X^(a) is a hydrogen or an optionally substitutedarylthio.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described in detail below. In the presentSpecification, the symbol “-” indicates a range having as minimum andmaximum the two numbers before and after it, inclusive.

The anthraquinone compound represented by formula (1) will be describedfirst.

In the formula (1), R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independentlyrepresents a hydrogen or substituent. Generalizing now the substituentas substituent group “V”, such substituent group “V” includes halogenatoms (e.g., chlorine, bromine, iodine, fluorine); mercapto group; cyanogroup; carboxyl group; phosphoric acid group; sulfonic acid group;hydroxyl group; carbamoyl groups having C₁₋₁₀, preferably C₂₋₈, morepreferably C₂₋₅ (e.g., methylcarbamoyl, ethylcarbamoyl,morpholinocarbamoyl); sulfamoyl groups having C₀₋₁₀, preferably C₂₋₈,and more preferably C₂₋₅ (e.g., methylsulfamoyl, ethylsulfamoyl,piperidinosulfamoyl); nitro group; alkoxy groups having C₁₋₂₀,preferably C₁₋₁₀, more preferably C₁₋₈ (e.g., methoxy, ethoxy,2-methoxyethoxy, 2-phenylethoxy); aryloxy groups having C₆₋₂₀,preferably C₆₋₁₂, more preferably C₆₋₁₀ (e.g., phenoxy, p-methylphenoxy,p-chlorophenoxy, naphthoxy); acyl groups having C₁₋₂₀, preferably C₂₋₁₂,more preferably C₂₋₈ (e.g., acetyl, benzoyl, trichloroacetyl); acyloxygroups having C₁₋₂₀, preferably C₂₋₁₂, more preferably C₂₋₈ (e.g.,acetyloxy, benzoyloxy); acylamino groups having C₁₋₂₀, preferably C₂₋₁₂,more preferably C₂₋₈ (e.g., acetylamino); sulfonyl groups having C₁₋₂₀,preferably C₁₋₁₀, more preferably C₁₋₈ (e.g., methanesulfonyl,ethanesulfonyl, benzenesulfonyl); sulfinyl groups having C₁₋₂₀,preferably C₁₋₁₀, more preferably C₁₋₈ (e.g., methanesulfinyl,ethanesulfinyl, benzenesulfinyl); sulfonylamino groups having C₁₋₂₀,preferably C₁₋₁₀, more preferably C₁₋₈ (e.g., methanesulfonylamino,ethanesulfonylamino, benzenesulfonylamino); amino groups having C₀₋₂₀,preferably C₁₋₁₂, more preferably C₁₋₈ (e.g., amino, methylamino,dimethylamino, benzylamino, anilino, diphenylamino, ethylamino,butylamino, phenetylamino, methoxyethylamino, ethoxyethylamino,p-methylphenylamino, m-methylphenylamino, o-methylphenylamino,p-chlorophenylamino, p-fluorophenylamino, p-trifluorophenylamino,o,o′-dimethylphenylamino); ammonium groups having C₀₋₁₅, preferablyC₃₋₁₀, more preferably C₃₋₆ (e.g., trimethylammonium, triethylammonium);hydrazino groups having C₀₋₁₅, preferably C₁₋₁₀, more preferably C₁₋₆(e.g., trimethylhydrazino); ureido groups having C₁₋₁₅, preferablyC₁₋₁₀, more preferably C₁₋₆ (e.g., ureido, N,N-dimethylureido); imidogroups having C₁₋₁₅, preferably C₁₋₁₀, more preferably C₁₋₆ (e.g.,succinimide); alkylthio groups having C₁₋₂₀, preferably C₁₋₁₂, morepreferably C₁₋₈ (e.g., methylthio, ethylthio, propylthio); arylthiogroups having C₆₋₈₀, preferably C₆₋₄₀, more preferably C₆₋₃₀ (e.g.,phenylthio, p-methylphenylthio, p-chlorophenylthio, 1-naphtylthio,2-naphtylthio, 4-propylcyclohexyl-4′-biphenylthio,4-butylcyclohexyl-4′-biphenylthio, 4-penthylcycloxexyl-4′-biphenylthio,4-propylphenyl-2-ethynyl-4′-biphenyltio); heteroarylthio groups havingC₁₋₈₀, preferably C₁₋₄₀, more preferably C₁₋₃₀ (e.g., 2-pyridylthio,3-pyridylthio, 4-pyridylthio, 2-quinolylthio, 2-furylthio,2-pyrrolylthio); alkoxycarbonyl groups having C₂₋₂₀, preferably C₂₋₁₂,more preferably C₂₋₈ (e.g., methoxycarbonyl, ethoxycarbonyl,2-benzyloxycarbonyl); aryloxycarbonyl groups having C₆₋₂₀, preferablyC₆₋₁₂, more preferably C₆₋₁₀ (e.g., phenoxycarbonyl); unsubstitutedalkyl groups having C₁₋₁₈, preferably C₁₋₁₀, more preferably C₁₋₅ (e.g.,methyl, ethyl, propyl, butyl); substituted alkyl groups having C₁₋₁₈,preferably C₁₋₁₀, more preferably C₁₋₅ {e.g., hydroxymethyl,trifluoromethyl, benzyl, carboxyethyl, ethoxycarbonylmethyl,acethylaminomethyl, also including unsaturated hydrocarbon groups havingC₂₋₁₈, preferably C₃₋₁₀, more preferably C₃₋₅ (e.g, vinyl, ethynyl,1-cyclohexyenyl, benzylidyne, benzyliden); substituted or unsubstitutedaryl groups having C₆₋₂₀, preferably C₆₋₁₅, more preferably C₆₋₁₀ (e.g.,phenyl, naphthyl, p-carboxyphenyl, p-nitrophenyl, 3,5-dichlorophenyl,p-cyanophenyl, m-fluorophenyl, p-tolyl); and substituted orunsubstituted heterocyclic groups having C₁₋₂₀, preferably C₂₋₁₀, morepreferably C₄₋₆ (e.g., pyridyl, 5-methylpyridyl, thienyl, furyl,morpholino, tetrahydrofurfuryl). Structures having condensed benzenerings or naphthalene rings are also allowable. Any substituents selectedfrom above substituent group “V” may be substituted by any substituentsselected from above substituent group “V”.

The substituent groups represented by R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ arepreferably alkyl groups, aryl groups, alkoxy groups, aryloxy groups,halogen atoms, amino, substituted amino groups, hydoroxy, alkylthiogroups or arylthio groups selected from the substituent group “V”.

It is preferable that R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ respectivelyrepresents a hydrogen atom, alkyl group, aryl group, alkoxy group,halogen atom, amino, substituted amino group, hydroxy, alkylthio groupor arylthio group; more preferable that R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸respectively represents a hydrogen atom, amino, substituted amino group,hydroxy, alkylthio group or arylthio group.

In the formula (1), Het represents an oxygen atom or sulfur atom,preferably a sulfur atom.

In the formula (1), B¹ and B² respectively represents an arylene,heteroarylene, cycloalkan-diyl or cycloalken-diyl group. The arylenegroups represented by B¹ and B² desirably have 6-20 carbon atoms.Preferred examples of the arylene groups are phenylene, naphtylene andanthrylene, especially preferred example is 1,4-phenylene. Theheteroarylene groups represented by B¹ and B² desirably have 1-20 carbonatoms. Preferred examples of the heteroarylene groups are pyridin-diyl,quinolin-diyl, isoquinolin-diyl, pyrimidylene, pyrazin-diyl,thiophenylene, furanylene, oxazolylene, thiazolylene, imidazolylene,pyrazolylene, oxadiazolylene, thiadiazolylene, triazolylenephenylene andheteroarylene groups having condensed structures thereof. Preferredexamples of the cycloalkan-diyl and cycloalken-diyl groups representedby B¹ and B² are cyclohexane-1,2-diyl, cyclohexane-1,3-diyl,cyclohexane-1,4-diyl, and cyclopentane-1,3-diyl, especially preferredexamples is (E)-cyclohexane-1,4-diyl.

B¹ and B² may have any substituent groups selected from the substituentgroup “V”. When p is 2 or more, in other words, plural B¹ are present,these may be the same or different. When r is 2 or more, in other words,plural B² are present, these may be the same or different.

In the formula (1), Q¹ represents a linkage group which may includecarbon atoms, nitorogen atoms, sulfur atoms or oxygen atoms. Thepreferred examples of the linkage group represented by Q¹ are alkylenegroups having C₁₋₂₀ (e.g., methylene, ethylene, propylene, butylenes,pentylene, cyclohexyl-diyl), alkenylene groups having C₂₋₂₀ (e.g.,ethenylene), alkynylene groups having C₂₋₂₀ (e.g., ethynylene), amido(—C(═O)NH—), oxy (—O—), carboxylato (—C(═O)O—), sulfoamido (—S(═O)₂NH—),sulfoxylato (—S(═O)₂O—), ureido (—NHC(═O)NH—), sulfonyl (—S(═O)₂—),sulfinyl (—S(═O)—), thioxy (—S—), carbonyl (—c(═O)—), —NR—(R representsa hydrogen atom, alkyl group or aryl group), azo (—N═N—), azoxy(—N₂(O)—), heterocyclo-diyl group (e.g., piperazine-1,4-diyl), and thegroups having C₀₋₂₀, which is composed by two or more groups selectedfrom above-mentioned examples.

Q¹ may have any substituent groups selected from the substituent group“V”. When q is 2 or more, in other words, plural Q¹ are present, thesemay be the same or different.

In the formula (1), C¹ is an optionally substituted alkyl, cycloalkyl,alkoxy, alkoxycarbonyl or acyloxy. Preferred examples of C¹ are alkyl orcycloalkyl groups having C₁₋₃₀, preferably C₁₋₁₂, more preferably C₁₋₈(e.g. ,methyl, ethyl, propyl, butyl, t-butyl, i-butyl, s-butyl, pentyl,t-pentyl, hexyl, heptyl, octyl, cyclohexyl, 4-methycyclohexyl,4-ethylcyclohexyl, 4-propylcyclohexyl, 4-butylcyclohexyl,4-pentylcyclohexyl, hydroxymethyl, trifluoromethyl, benzyl); alkoxygroups having C₁₋₂₀, preferably C₂₋₁₂, more preferably C₂₋₈ (e.g.,methoxy, ethoxy, 2-methoxyethoxy, 2-phenylethoxy); acyloxy groups havingC₁₋₂₀, preferably C₂₋₁₂, more preferably C₂₋₈ (e.g., acethyloxy,benzoyloxy); alkoxycarbonyl groups having C₂₋₂₀, preferably C₂₋₁₂, morepreferably C₂₋₈ (e.g., methoxycarbonyl, ethoxycarbonyl,2-benzyloxycarbonyl). C¹ is more preferably an optionally substitutedalkyl or alkoxy, further more preferably ethyl, propyl, butyl, pentyl,hexyl or trifuloromethoxy.

C¹ may have any substituent groups selected from the substituent group“V”.

p, q and r respectively represents a number from 0 to 5 and n is anumber from 1 to 3, satisfying 3≦(p+r)×n≦10. When n is 2 or more,namely, plural {(B¹)_(p)-(Q¹)_(q)-(B²)_(r)} are present, these plural{(B¹)_(p)-(Q¹)_(q)-(B²)_(r)} may be the same or different.

Preferred combinations of p, q and rare (1) to (13) as shown below:

(1) P=3, q=0, r=1 and n=1;

(2) P=4, q=0, r=0 and n=1;

(3) P=5, q=0, r=0 and n=1;

(4) P=2, q=1, r=1 and n=1;

(5) P=1, q=1, r=2 and n=1;

(6) P=3, q=1, r=1 and n=1;

(7) P=1, q=1, r=3 and n=1;

(8) P=2, q=1, r=2 and n=1;

(9) P=1, q=1, r=1 and n=3;

(10) P=0, q=1, r=3 and n=1;

(11) P=0, q=1, r=2 and n=2;

(12) P=1, q=1, r=2 and n=2;

(13) P=2, q=1, r=1 and n=2.

Especially preferred combinations are (1) P=3, q=0, r=1 and n=1; (2)P=4, q=0, r=0 and n=1; (4) P=2, q=1, r=1 and n=1.

The substituent represented by the formula of-{(B¹)_(p)-(Q¹)_(q)-(B²)_(r)}_(n)-C¹ preferably containing structuresexhibiting liquid crystallinity. The structures may exhibit any kind ofliquid crystallinity, however, preferably nematic, smectic, or discoticliquid crystallinity, more preferably nematic liquid crystallinity.Examples of structures exhibiting liquid crystals are shown in“Bunshikouzou to ekishosei (Molecular Structure and LiquidCrystallinity)”, third chapter of “Ekisho Binran (Handbook of LiquidCrystal)” published by Maruzen in 2000, edited by Society of editinghandbook of Liquid crystal.

Specific examples of the substituent represented by the formula of-{(B¹)_(p)-(Q¹)_(q)-(B²)_(r)}_(n)-C¹ will be listed below, which by nomeans restricts the present invention. In the following formulae, wavelines denote portions of attaching to Het.

In the formula (1), at least one of R²-R⁸ may be a substituentrepresented by the formula of -{(B¹)_(p)-(Q¹)_(q)-(B²)_(r)}_(n)-C¹. Atleast one of R⁴, R⁵ and R⁸ is preferably a substituent represented bythe formula of -{(B¹)_(p)-(Q¹)_(q)-(B²)_(r)}_(n)-C¹. A number ofsubstituent “-{(B¹)_(p)-(Q¹)_(q)-(B²)_(r)}_(n)-C¹” contained in ananthraquinone compound represented by the formula (1) may be 1-8,preferably 1-6, more preferably 1-4.

As one preferred embodiment of this invention, there is provided theanthraquinone compound represented by a formula (2) bellow:

In the formula (2), S is a sulfur atom; and X¹, Y¹ and Z¹ eachindependently represents a hydrogen atom, halogen atom, hydroxyl,optionally substituted amino, arylthio or heteroarylthio, provided X¹,Y¹ and Z¹ are not all hydrogen. Preferred examples of amino groupsrepresented by X¹, Y¹ and Z¹ are non-substituted amino (—NH₂), arylaminogroups, heteroarylamino groups, acylamino groups and alkylamino groups,more preferred examples are arylamino groups, heteroarylamino groups,acylamino groups and alkylamino groups.

Aryl groups included in the arylamino groups represented by X¹, Y¹ andZ¹ have preferably C₆₋₃₀, more preferably C₆₋₁₅, further more preferablyC₆₋₁₂. Preferable examples of aryl groups included in the arylaminogroups are p-carboxyphenyl, p-nitrophenyl, p-chlorophenyl,3,5-dichlorophenyl, p-cyanophenyl, m-fluorophenyl, p-toryl,p-cyclohexylphenyl. Aryl groups included in the arylamino groups mayhave any substituent selected from the substituent group “V”.

Heteroaryl groups included in the heteroarylamino groups represented byX¹, Y¹ and Z¹ have preferably C₁₋₂₀, more preferably C₂₋₁₅, further morepreferably C₄₋₁₀. Preferred examples of heteroaryl groups included inthe hetreroarylamino groups are pyridyl, 5-methylpyridyl, thienyl andfuryl. Heteroaryl groups included in the heteroarylamino groups may haveany substituent selected from the substituent group “V”.

Acyl groups included in the acylamino groups represented by X¹, Y¹ andZ¹ have preferably C₁₋₂₀, more preferably C₂₋₁₂, further more preferablyC₂₋₈. Preferred examples of acyl groups included in the acylamino groupsare acethyl, benzoyl and trichloroacethyl. Acyl groups included in theacylamino groups may have any substituent selected from the substituentgroup “V”.

Alkyl groups included in the alkylamino groups represented by X¹, Y¹ andZ¹ have preferably C₁₋₂₀, more preferably C₂₋₁₅, further more preferablyC₂₋₁₀. Preferred examples of alkyl groups included in the alkylaminogroups are methyl, ethyl, propyl, butyl, pentyl, hexyl, phenethyl,methoxyethyl, fluoroethyl and chloroethyl. Alkyl groups included in thealkylamino groups may have any substituent selected from the substituentgroup “V”.

Aryl groups included in arylthio groups represented by X¹, Y¹ and Z¹have preferably C₆₋₃₀, more preferably C₆₋₂₅, further preferably C₆₋₂₀.Preferred examples of aryl groups included in the arylthio groups arephenyl, naphthyl, p-carboxyphenyl, p-nitrophenyl, p-chlorophenyl,3,5-dichlorophenyl, p-cyanophenyl, m-fluorophenyl, p-tryl,p-cyclohexylphenyl, p-(4-buthylcyclohexyl)phenyl,p-(p-hexylphenyl)phenyl and p-(p-(4-penthylcyclohexyl)phenyl)phenyl.Aryl groups included in the arylthio groups may have any substituentthio, selected from the substituent group “V”.

Heteroaryl groups included in the heteroarylthio groups represented byX¹, Y¹ and Z¹ have preferably C₁₋₂₀, more preferably C₂₋₁₅, further morepreferably C₄₋₁₀. Preferable examples of heteroaryl groups included inthe hetreroarylthio groups are pyridyl, 5-methylpyridyl, thienyl andfuryl. Heteroaryl groups included in the heteroarylthio groups may haveany substituent selected from the substituent group “V”.

It is preferable that X¹, Y¹ and Z¹ each independently represents ahydrogen, chlorine, bromine, amino(—NH₂), optionally substitutedalkylamino, optionally substituted arylamino, optionally substitutedarylthio or optionally substituted heteroarylthio; more preferable thatX¹, Y¹ and Z¹ each independently represents a hydrogen, optionallysubstituted alkylamino, optionally substituted arylthio or optionallysubstituted heteroarylthio. However, X¹, Y¹ and Z¹ are not all hydrogen.

In the formula (2), A, B and C each independently represents anoptionally substituted arylene, heteroarylene or cyclohexandiyl.

The arylene groups have preferably C₆₋₂₀. Arylene groups may have anysubstituent selected from the substituent group “V”. Preferred examplesof the arylene groups are optionally substituted, phenylene, naphthyleneand anthrathenylene.

The heteroarylene groups have preferably C₂₋₂₀. Heteroarylene groups mayhave any substituent selected from the substituent group “V”. Preferredexamples of the heteroarylene groups are optionally substituted,pyridin-diyl, quinolin-diyl, isoquinolin-diyl, pyrimidylene,pyrazin-diyl, thiophenylene, furanylene, oxazolylene, thiazolylene,imidazolylene, pyrazolylene, oxadiazolylene, thiadiazolylene,triazolylenephenylene and any bivalent groups of fused aromatic ringsformed by condensation thereof.

The cyclohexandiyl groups have any substituent selected from thesubstituent group “V”. One preferred example of the cyclohexandiylgroups is (E)-cyclohexan-1,4-diyl.

It is preferable that A is an optionally substituted phenylene, morepreferably 1,4-phenylene; and that Either of B and C is acyclohexandiyl, more preferably B is an optionally substituted aryleneand C is a cyclohexandiyl, especially preferably B is a 1,4-phenyleneand C is a (E)-cyclohexandiyl-1,4-diyl.

In the formula (2), D represents an optionally substituted alkyl,cycloalkyl, alkoxy, alkoxycarbonyl or acyloxy. They may have anysubstituent selected from the substituent group “V”. Preferred examplesof D are alkyl and cycloalkyl groups having C₁₋₃₀, preferably C₁₋₁₂,more preferably C₁₋₈ (e.g., methyl, ethyl, propyl, butyl, t-butyl,i-butyl, s-butyl, pentyl, t-pentyl, hexyl, heptyl, octyl, cyclohexyl,4-methylcyclohexyl, 4-ethylcyclohexyl, 4-propylcyclohexyl,4-butylcyclohexyl, 4-pentylcyclohexyl, hydroxymethyl, trifluoromethyl,benzyl); alkoxy groups having C₁₋₂₀, preferably C₁₋₁₀, more preferablyC₁₋₈ (e.g., methoxy, ethoxy, 2-methoxyethoxy, 2-phenylethoxy); acyloxygroups having C₁₋₂₀, preferably C₂₋₁₂, more preferably C₂₋₈ (e.g.,acethyloxy, benzoyloxy); alkoxycarbonyl groups having C₂₋₂₀, preferablyC₂₋₁₂, more preferably C₂₋₈ (e.g., methoxycarbonyl, ethoxycarbonyl,2-benzyloxycarbonyl). D is more preferably an alkyl or alkoxy group,further more preferably ethyl, propyl, buthyl, penthyl hexyl ortrifluoromethoxy.

In the formula (2) X¹, Y¹, Z¹, A, B, C and D each may have anysubstituent, typical examples of it may be belong to the substituentgroup “V”.

As another preferred embodiment of this invention, there is provided theanthraquinone compound represented by any one of formulae (3)-(6) below:

In the formulae (3)-(6), Z² to Z⁸ each independently represents anoptionally substituted arylthio or heteroarylthio. In the formulae(3)-(6), S, A, C and D each represents the same as in the formula (2),and also the preferred examples thereof may be the same.

Aryl groups included in the arylthio groups represented by Z² to Z⁸ havepreferably C₆₋₃₀, more preferably C₆₋₂₅, further more preferably C₆₋₂₀.Preferred examples of aryl groups included in the arylthio groups arephenyl, naphthyl, p-carboxyphenyl, p-nitrophenyl, p-chlorophenyl,3,5-dichlorophenyl, p-cyanophenyl, m-fluorophenyl, p-tryl,p-cyclohexyl-phenyl, p-(4-buthylcyclohexyl)phenyl,p-(p-hexylphenyl)phenyl and p-(p-(4-penthylcyclohexyl)phenyl)phenyl.

Heteroaryl groups included in the heteroarylthio groups represented byZ² to Z⁸ have preferably C₁₋₂₀, more preferably C₂₋₁₅, further morepreferably C₄₋₁₀. Preferred examples of heteroaryl groups included inthe hetreroarylamino groups are pyridyl, 5-methylpyridyl, thienyl andfuryl.

Aryl and heteroaryl groups included in the arylthio and heteroarylthioeach may have any substituent selected from the substituent group “V”.

Absorption peaks of compounds represented by formulae (3) to (6) will beexplained bellow.

Generally, compounds represented by each the formula (3) and (4) exhibitat least one absorption maximum at the range of 430 nm-480 nm; compoundsrepresented by the formula (5) exhibit at least one absorption maximumat the range of 480 nm-540 nm; and compounds represented by the formula(6) exhibit at least one absorption maximum at the range of 500 nm-580nm. Namely, it is shown a rough tendency that compounds represented byeach the formula (3) (or (4)), (5) and (6) are shifted long-wavelengthin the sequence.

As another preferred embodiment of this invention, there is provided theanthraquinone compound represented by formula (1-a) below:

In the formula (1-a), s, A, B and C each represents the same as in theformula (2), and also the preferred examples thereof may be the same.

In the formula (1-a), X^(a), Y^(a) and Z^(a) each represents a hydrogen,optionally substituted arylthio or heteroarylthio group, provided atleast one of X^(a), Y^(a) and Z^(a) represents an arylthio group.Arylthio and heteroarylthio groups represented by X^(a), Y^(a) and Z^(a)maybe the same as those represented by Z² to Z⁸ in the formula (3) to(6), and also the specific and preferred examples thereof may be thesame.

As preferred embodiments of the anthraquinone compound represented bythe formula (1-a), there are provided an anthraquinone compoundrepresented by following formula (2-a) that is equal to the formula(1-a) wherein X^(a) and Z^(a) are hydrogen and Y^(a) is an optionallyarylthio group; and an anthraquinone compound represented by followingformula (3-a) that is equal to the formula (1-a) wherein X^(a), Y^(a)and Z^(a) are all optionally substituted arylthio groups.

In the formula (2-a), S, A, B, C, and D are each represents the same asin the formula (1-a), and also the preferred examples thereof may be thesame. Y^(2a) represents an optionally substituted arylthio group. Thearylthio group represented by Y^(2a) may be the same as thoserepresented by X^(a), Y^(a) and Z^(a) in the formula (1-a), and also thespecific and preferred examples thereof may be the same.

In the formula (3-a), S, A, B, C, and D are each represents the same asin the formula (1-a), and also the preferred examples thereof maybe thesame. Y^(2a) represents an optionally substituted arylthio group. Thearylthio group represented by Y^(2a) may be the same as thoserepresented by X^(a), Y^(a) and Z^(a) in the formula (1-a), and also thespecific and preferred examples thereof may be the same.

Particular preferable examples of anthraquinone compounds represented bythe formula (1-a) is an anthraquinone compound wherein X^(a) and Z^(a)are both hydrogen and Y^(a) is an optionally substituted phenylthiogroup (more preferably 4-substituted phenylthio group); and ananthraquinone compound wherein X^(a), Y^(a) and Z^(a) each independentlyrepresents an optionally substituted phenylthio group (more preferably4-substituted phenylthio group). Namely, former is an anthraquinonecompound represented by the formula (2-a) wherein Y^(2a) is anoptionally substituted arylthio group (more preferably 4-substitutedphenylthio group), and latter is an anthraquinone compound representedby the formula (3-a) wherein X^(3a), Y^(3a) and Z^(3a) eachindependently represents an optionally substituted phenylthio group(more preferably 4-substituted phenylthio group).

Specific preferred examples of the anthraquinone compound represented bythe formula (1) are given below; however, the present invention is in noway limited to these specific examples.

The anthraquinone compounds represented by the formula (1) can besynthesized based on methods disclosed in “Dichroic Dyes for LiquidCrystal Display” (written by a. V. Ivashchenko, published by CRC, in1994), “Sohsetsu Gohsei Senryou (Review of Synthesized Dyes)” (writtenby Hiroshi Horiguchi, published by Sankyo Syuppan, in 1968) andliteratures cited therein.

The liquid crystal composition of the present invention is characterizedin that containing an anthraquinone compound represented by the formula(1), which may occasionally be referred to as “anthraquinone compoundsof the present invention”. The anthraquinone compound of the presentinvention has a large solubility in host liquid crystals, which can thuscontribute improvement of order parameter of the liquid crystalcomposition. In particular, the anthraquinone compound of the presentinvention is characterized by a high solubility in fluorine-substitutedhost liquid crystal, which may be suitable for TFT driving. Furthermore,using such compound as a dichroic dye for a guest-host mode liquidcrystal display will successfully improve contrast.

For the liquid crystal composition of the present invention, theanthraquinone compound may be used individually, or in any combinationsof two or more species. For the case of using two or more species, twoor more compounds of the present invention may be mixed, or the compoundof the present invention may be mixed with other known dichroic dye.Description of such known dichroic dyes available for the mixed use aretypically found in “Dichroic Dyes for Liquid Crystal Display”, writtenby A. V. Ivashchenko, published by CRC, 1994. In order to apply theliquid crystal composition of the present invention to a black-and-whitedisplay, it is preferable to use two or more dichroic dyes as mixed sothat they can cooperatively absorb the light over the entire visiblewavelength range.

While there is no specific limitation on the host liquid crystal (liquidcrystal compound) available for the composition of the presentinvention, typical examples thereof include those exhibiting nematicphase or smectic phase. Specific examples thereof include azomethinecompounds, cyanobiphenyl compounds, cyanophenyl esters,fluorine-substituted phenyl esters, cyclohexanecarboxylic acid phenylesters, fluorine-substituted cyclohexanecarboxylic acid phenyl esters,cyanophenylcyclohexanes, fluorine-substituted phenylcyclohexanes,cyano-substituted phenylpyrimidines, fluorine-substitutedphenylpyrimidines, alkoxy-substituted phenylpyrimidines,fluorine-substituted-alkoxy-substituted phenylpyrimidines,phenyldioxanes, tolan compounds, fluorine-substituted tolan compoundsand alkenylcyclohexyl benzonitriles. Available examples of the liquidcrystal compounds are found in “Ekisho Debaisu Handobukku (LiquidCrystal Device Handbook), edited by No. 142 Committee of Japan Societyfor the Promotion of Science, published by the Nikkan Kogyo Shimbun,Ltd., 1989, p. 154-192, and p. 715-722. The fluorine-substituted hostliquid crystal such as MLC-6267, 6284, 6287, 6288, 6406, 6422, 6423,6425, 6435, 6437, 7700, 7800, 9000, 9100, 9200, 9300, 10000, 12200,ZLI-4692 (the above are supplied by Merck), LIXON 5036XX, 5037XX,5039XX, 5040XX, 5041XX, (the above are supplied by Chisso) etc., whichis suitable for TFT driving, is preferred for this invention.

The liquid crystal composition of the present invention may be addedwith a compound showing no liquid crystalline property in order toadjust physical properties of the host liquid crystal (typically inorder to adjust the temperature range, in which the liquid crystal phaseappears, to a desirable range). It is also allowable to add othercompounds such as chiral compound, UV absorber and antioxidant. Typicalexamples thereof relate to chiral agents for twisted-nematic (TN) andsuper-twisted-nematic (STN) liquid crystals, which can typically befound in “Ekisho Debaisu Handobukku (Liquid Crystal Device Handbook),edited by No. 142 Committee of Japan Society for the Promotion ofScience, published by the Nikkan Kogyo Shimbun, Ltd., 1989, p. 199-202.

While there is no specific limitation on the content of the host liquidcrystal and the compound of the present invention, the content of thecompound of the present invention is preferably 0.1 to 15 wt % withrespect to the content of the host liquid crystal, and more preferably0.5 to 6 wt %.

The liquid crystal composition of the present invention can be preparedby dissolving the compound of the present invention into the host liquidcrystal. The dissolution can be attained with the aid of mechanicalstirring, heating, ultrasonic vibration and any combinations thereof.

The guest-host-type liquid crystal cell of the present invention has aliquid crystal layer containing the liquid crystal composition of thepresent invention.

One embodiment of the present invention is a liquid crystal cellcomprising a pair of electrode substrates and a liquid crystal layersandwiched between such electrode substrates, which contains the liquidcrystal composition of the present invention. The electrode substrategenerally comprises a glass substrate or plastic substrate, and anelectrode layer formed thereon. Materials available for composing theplastic substrate include acryl resin, polycarbonate resin, epoxy resinand so forth. Available examples of such substrate are typically foundin “Ekisho Debaisu Handobukku (Liquid Crystal Device Handbook), editedby No. 142 Committee of Japan Society for the Promotion of Science,published by the Nikkan Kogyo Shimbun, Ltd., 1989, p. 218-231. Theelectrode layer formed on the substrate is preferably a transparentelectrode layer. Materials available for composing such electrode layerinclude indium oxide, indium tin oxide (ITO), tin oxide and so forth.Available examples of the transparent electrode are typically found in“Ekisho Debaisu Handobukku (Liquid Crystal Device Handbook), edited byNo. 142 Committee of Japan Society for the Promotion of Science,published by the Nikkan Kogyo Shimbun, Ltd., 1989, p. 232-239.

The surface of the substrate to be brought into contact with the liquidcrystal layer preferably has formed thereon a layer subjected totreatment for controlling orientation of the liquid crystal molecules(alignment film). The treatment can be effected by coating of aquaternary ammonium salt solution, rubbing a coated polyimide film, byoblique vapor deposition of SiO_(x), and photo irradiation based onphoto-isomerization reaction. Available examples of the alignment filmcan typically be found in “Ekisho Debaisu Handobukku (Liquid CrystalDevice Handbook), edited by No. 142 Committee of Japan Society for thePromotion of Science, published by the Nikkan Kogyo Shimbun, Ltd.,1989), p. 240-256.

The liquid crystal cell of the present invention can be fabricated byopposing a pair of substrates at a distance of 1 to 50 μm as beingtypically interposed with a spacer, and filling the liquid crystalcomposition of the present invention in the space formed between suchsubstrates. Available examples of the spacer can typically be found in“Ekisho Debaisu Handobukku (Liquid Crystal Device Handbook), edited byNo. 142 Committee of Japan Society for the Promotion of Science,published by the Nikkan Kogyo Shimbun, Ltd., 1989), p. 257-262.

The liquid crystal cell of the present invention can be driven based onsimple matrix driving system or active matrix driving system using thinfilm transistors (TFT) or the like. Examples of the driving systemsapplicable to the liquid crystal cell of the present invention cantypically be found in “Ekisho Debaisu Handobukku (Liquid Crystal DeviceHandbook), edited by No. 142 Committee of Japan Society for thePromotion of Science, published by the Nikkan Kogyo Shimbun, Ltd.,1989), p. 387-460.

The liquid crystal cell of the present invention can be applicable toliquid crystal display. While the display modes thereof are notspecifically limited, representative systems described in “EkishoDebaisu Handobukku (Liquid Crystal Device Handbook), edited by No. 142Committee of Japan Society for the Promotion of Science, published bythe Nikkan Kogyo Shimbun, Ltd., 1989, p. 309 include those based on (1)homogeneous orientation and (2) homeotropic orientation, both of whichbeing classified in the guest-host-type; and (3) focalconic orientationand (4) homeotropic orientation, both of which being classified inWhite-Taylor-type (phase transition); (5) combination with STN crystal;and (6) combination with ferroelectric liquid crystal (FLC). Guest-host(GH) mode display is also available, and “Hansha-gata Kara LCD SogoGijutsu (General Technologies of Reflection-type Color LCD)”, supervisedby Tatsuo Uchida, published by CMC, 1999, Chapter 2-1 “GH-mode,Reflective mode Color LCD”, p. 15-16 describes specific examplesthereof, which include those of (1) Heilmeier mode, (2) quarter-waveplate mode, (3) double layer mode, (4) phase transition mode, and (5)polymer-dispersed liquid crystal (PDLC) mode.

The liquid crystal cell of the present invention may be applied in aliquid crystal display of multiple layered GH mode such as disclosed inJP-A-10-67990, JP-A-10-239702, JP-A-10-133223, JP-A-10-339881,JP-A-11-52411, JP-A-11-64880 and JP-A-2000-221538(the term “JP-A” asused herein means an “unexamined published Japanese patentapplication”), and in a liquid crystal display of GH mode usingmicrocapsules such as disclosed in JP-A-11-24090. Furthermore, theliquid crystal cell may be applied in a reflective mode liquid crystaldisplay such as disclosed in JP-A-6-235931, JP-A-6-235940,JP-A-6-265859, JP-A-7-56174, JP-A-9-146124, JP-A-9-197388,JP-A-10-20346, JP-A-10-31207, JP-A-10-31216, JP-A-10-31231,JP-A-10-31232, JP-A-10-31233, JP-A-10-31234, JP-A-10-82986,JP-A-10-90674, JP-A-10-111513, JP-A-10-111523, JP-A-10-123509,JP-A-10-123510, JP-A-10-206851, JP-A-10-253993, JP-A-10-268300,JP-A-11-149252 and JP-A-2000-2874; and in a liquid polymer-dispersedliquid crystal (PDLC) mode such as disclosed in JP-A-5-61025,JP-A-5-265053, JP-A-6-3691, JP-A-6-23061, JP-A-5-203940, JP-A-6-242423,JP-A-6-289376, JP-A-8-278490 and JP-A-9-813174.

The liquid crystal composition of the present invention is alsoapplicable to spatial light modulator, and liquid crystal display ofoptically-addressed or thermally-addressed type.

EXAMPLES

The present invention will be specifically explained with reference tothe following examples. The materials, regents, ratios, procedures andso forth shown in the following examples can be optionally changed solong as such change does not depart from the spirit of the presentinvention. Therefore, the scope of the present invention is not limitedby the following examples.

Example 1 Exemplary Synthesis of Compound (2)

Compound (2) was synthesized according to the following route.

50 ml of dimethylamide was added to a mixture containing 5 g ofIntermediate (1), 4.2 g of Intermediate (2) and 3.4 g of potassiumcarbonate, and the obtained mixture was stirred for 2 hours at 100° C.The reaction mixture was cooled to room temperature, added with water,organic components contained therein was then extracted with chloroform.The volatile component in the chloroform phase was removed bydistillation in vacuo, and the obtained residue was purified by silicagel chromatography (eluted with chloroform-hexane), to thereby obtain5.6 g of target Compound (2) as yellow powders. Properties of obtainedCompound (2) are listed below.

m.p. 207-209° C.

H-NMR(CDCl₃): 8.15(2H,m), 7.69(4H,dd), 7.58(2H,d), 7.53(2H,d),7.48(2H,d), 7.33(4H,m), 7.18(1H,dd), 7.09(1H,dd), 2.69(2H,t),2.54(1H,tt), 1.92(4H,m), 1.68(2H,m), 1.50(1H,m), 1.18-1.42(16H,m),1.09(2H,m), 0.90(6H,m).

Example 2 Exemplary Synthesis of Compound (39)

Compound (39) was synthesized according to the following route.

50 ml of dimethylamide was added to a mixture containing 3.8 g ofIntermediate (3), 3.3 g of Intermediate (2) and 6.3 g of potassiumcarbonate, and the obtained mixture was stirred for 2 hours at 100° C.The reaction mixture was cooled to room temperature, added with water,organic components contained therein was then extracted with chloroform.The volatile component in the chloroform phase was removed bydistillation in vacuo, and the obtained residue was purified by silicagel chromatography (eluted with chloroform-hexane), to thereby obtain1.1 g of target Compound (39) as purplish red colorpowders. Propertiesof obtained Compound (39) are listed below.

m.p. 300° C. or above.

NMR(CDCl₃): 7.63(8H, br), 7.47-7.56(8H, m), 7.43(4H, d), 7.29(4H, d),6.93(4H, m), 2.51(2H, m), 1.91(8H, m), 1.43-1.53(2H, m), 1.16-1.43(38H,m), 1.07(4H, m), 0.91(6H, t).

Example 3 Exemplary Synthesis of Compound (33)

Compound (33) was synthesized according to the following route.

200 ml of dimethylamide was added to a mixture containing 2.0 g ofIntermediate (4), 1.1 g of Intermediate (5) and 2.7 g of potassiumcarbonate, and the obtained mixture was stirred for 2 hours at 100° C.The reaction mixture was cooled by room temperature, added with water,organic components contained therein was then extracted with chloroform.The volatile component in the chloroform phase was removed bydistillation in vacuo, and the obtained residue was purified by silicagel chromatography (eluted with chloroform-hexane), to thereby obtain1.7 g of target Compound (33) as purplish red color powders. Propertiesof obtained Compound (33) are listed below.

m.p. 272° C.

NMR(CDCl₃): 7.65(4H, s), 7.57-7.36(16H, m), 6.92(4H, s), 2.51(1H, m),1.91(4H, m), 1.43-1.53(1H, m), 1.16-1.43(27H, m), 1.07(2H, m), 0.91(3H,t).

Example 4 Exemplary Synthesis of Compound (85)

Compound (85) was synthesized according to the following route.

(Exemplary Synthesis of Compound (C-2))

A mixture 61.9 g of Compound (B-2) (provided by Kanto Kagaku), 34.2 g ofPhenylboronic acid (provided by Tokyo Kasei Kogyo Co., Ltd.), 10.5 g oftriphenyl phosphine, 4.49 g of palladium acetate and 260 g of potassiumcarbonate was treated with a mixture of 1.2 L toluene and 0.6 L of waterat 100° C. on an oil bath for 2 hours under stirring and a nitrogenatmosphere. The obtained reaction solution was cooled to roomtemperature, filtered through Celite, and organic component containedtherein was extracted with ethyl acetate. The volatile component in theethyl acetate phase was removed by distillation in vacuo, and theobtained residue was purified by silica gel chromatography (eluted withhexane), to thereby obtain 47.6 g (in a 78% yield) of target Compound(C-2) as colorless crystals.

(Exemplary Synthesis of Intermediate (2))

15.2 mL of chlorosulfonic acid was added to 200 mL of methylene chloridesolution containing 51.6 g of Compound (2), the obtained mixture wasstirred for 45 minute, and throughout the adding and stirring, an innertemperature was kept between 10 to 15° C. After 28 mL of chloroform and84 mL of N,N-dimethylacetamide were added to the reaction solution, 31.4mL of phosphorus oxycloride was added dropwise to the reaction solution,and then the inner temperature of the reaction solution raised to 40° C.The obtained reaction solution was stirred for an hour at 40° C. of theinner temperature, poured into 136 g of ices, and 25 mL of concentratedsulfuric acid was added dropwise to the reaction solution. 40.4 g ofzinc was added slowly to the reaction solution heated to 20° C. of theinner temperarute with stirring and the solution was stirred for 3 hoursat 80° C. of the inner temperature. Ethyl acetate was added to theobtained reaction solution cooled to room temperature, and the inorganiccomponent contained therein was removed by filtration and the organiccomponent contained therein was extracted by ethyl acetate. The volatilecomponent in the ethyl acetate phase was removed by distillation invacuo, and the obtained residue was purified by silica gelchromatography (eluted with chloroform), to thereby obtain 29.5 g (in a54% yield) of target Intermediate (2) as colorless crystals (showingm.p. 133° C.).

(Exemplary Synthesis of Intermediate (6))

2.9 g of sodium nitrite and 4.7 g of boric acid were added to 100 ml ofa sulfuric acid solution containing 10.0 g of1-chloro-5-nitoroanthraquinone, which was synthesized based on a methoddisclosed in U.S. Pat. No. 2,417,027, and the obtained mixture washeated to outer temperature of 200° C. on an oil bath for 4 hours understirring. The obtained reaction solution was poured into ice water, tothereby yield products as crude crystal. The crude crystal was purifiedby silica gel chromatography, to thereby obtain 64.5 g of Intermediate(6).

(Exemplary Synthesis of Intermediate (7))

50 ml of dimethylformamide solution containing 1.0 g of Intermediate(2), 2.5 g of Intermediate (6) and 3.5 g of potassium carbonate washeated to outer temperature of 150° C. on an oil bath for 7 hours understirring. The obtained reaction solution was poured into dilutehydrochloric acid, to thereby yield products as crude crystal. The crudecrystal was purified by silica gel chromatography, to thereby obtain 2.5g of Intermediate (7) as orange crystal.

(Exemplary Synthesis of Intermediate (8))

1.9 g of tin was added to a mixture containing 1.0 g of Intermediate(7), 32 ml of acetic acid and 5.5 ml of hydrochloric acid, and theobtained mixture was heated to outer temperature of 120° C. on an oilbath for 18 hours under stirring. Water was added to the obtainedreaction solution, to thereby yield products as crude crystal. The crudecrystal was purified by silica gel chromatography, to thereby obtain 0.6g of Intermediate (8).

(Exemplary Synthesis of Intermediate (85))

A mixture containing 0.2 g of Intermediate (8) and 10 ml of ethanolsolution containing 1 ml of buthylamine was refluxed with stirring for18 hours. The obtained reaction solution was poured into dilutehydrochloric acid, to thereby yield products as crude crystal. The crudecrystal was purified by silica gel chromatography, to thereby obtain0.12 g of Compound (85) as blue crystal.

Absorption maximum=610 nm and 670 nm (in chloroform)

The intensity of an absorption peak at 450 nm is 2% of that at 670 nm,it suggests that Compound (85) is a cyan dye which exhibits a much weakcounter-absorption at yellow range.

Example 5

Each of the compounds (some are compounds of the present invention, andanother are comparative compounds) listed in Table 1 below in an amountof 1.0 mg was mixed with each 50 mg, 200 mg and 100 mg of a liquidcrystal ZLI-1132 (trade name, a product of E. Merck), and the mixtureswere heated to 80° C. and subsequently cooled to room temperature.According to observation how each compounds was dissolved in liquidcrystal, the solubilities of compounds were listed in Table 1. “>2%”means that compounds were fully dissolved in 50 mg, “1-2%” means thatcompounds were dissolved in 100 mg and not fully in 50 mg, “0.5-1%”means that compounds were fully dissolved in 200 mg and not fully in 100mg, and “<0.5%” means that compounds were not fully dissolved in even200 mg and insoluble matter were found in liquid crystal. Samples havinghighest concentration of each compounds listed in Table 1 were used forproducing liquid crystal cells as liquid crystal components.

Each of obtained liquid crystal compositions was then filled in acommercial liquid crystal cell to thereby fabricate a guest-host-typeliquid crystal cell or a comparative liquid crystal cell. Each of liquidcrystal cells employed herein was a product of E. H. C. Corporation,which comprises a pair of glass plates (0.7 mm thick) having formedthereon ITO transparent electrode layers and polyimide alignment films(patterned in parallel by rubbing treatment), has a cell gap of 8 μm,and has a epoxy resin seal.

Each of thus fabricated liquid crystal cells was respectively irradiatedwith polarized lights in parallel to and perpendicular to the directionof rubbing, and respective absorption spectra (A∥ and A⊥) were measuredusing a spectrophotometer Model UV3100 (product of ShimadzuCorporation). Based on A∥ and A⊥, the order parameter S was calculatedusing the equation 1 below. Thus calculated order parameters S werelisted in Table 1 together with absorption maximum wavelengths (λ_(max))and solubilities.S=(A∥−A⊥)/(A∥+2×A⊥)  quation 1

TABLE 1 Order Anthraquinone λmax Parameter Compound Solubility (nm) SCompound (1)   >2% 455 0.82 Compound (2)   >2% 455 0.83 Compound (3)  >2% 450 0.81 Compound (14)   1-2% 450 0.87 Compound (16)   >2% 4550.81 Compound (17)   >2% 455 0.82 Compound (24)   >2% 470 0.81 Compound(27)   >2% 520 0.81 Compound (39)   1-2% 550 0.81 Compound (43)   >2%550 0.82 Compound (46)   1-2% 550 0.81 Compound (54)   >2% 660 0.82Compound (63)   >2% 455 0.84 Compound (85)   >2% 670 0.81 Comparative0.5-1% 600 0.8 Compound (1) Comparative 0.5-1% 455 0.77 Compound (2)Comparative   1-2% 455 0.73 Compound (3) Comparative 0.5-1% 555 0.75Compound (4) Comparative Compound (1)

(This is disclosed in JP-A-59-22964 as Compound 99.) ComparativeCompound (2)

(This is disclosed in JP-A-62-64886 as a compound represented by formula(III).) Comparative Compound (3)

(This is disclosed in JP-A-2-178390 as Compound I-8.) ComparativeCompound (4)

This is disclosed in JP-A-10-260386 as Compoud IV-2.)

As shown data in Table 1, the compounds of the present invention exhibitnot only large order parameters but also high solubilities. On the otherhand, none of Comparative compounds can achieve a balance between largeorder parameter and high solubility like the compounds of the presentinvention. To put it concretely, Comparative compound (1) exhibits arelatively large parameter, but a low solubility; Comparative compound(3) exhibits a relatively high solubility, but a small order parameter;and Comparative compound (2) and (4) exhibit small parameters and lowsolubilities.

INDUSTRIAL APPLICABILITY

The present invention as described above can provide a liquid crystalcomposition and a liquid crystal cell which can contribute toimprovement of displaying contrast and bring about high optical density,when employed in displaying devices. The present invention can alsoprovide novel anthraquinone dyes which are useful as dichroic dyes, andin especial novel anthraquinone dyes bringing about high orderparameters and having high solubilities for host crystal liquid.

1. The liquid crystal composition comprising at least one liquid crystalcompound and at least one anthraquinone compound represented by formula(2) below:

where S is a sulfur atom; A, B and C each independently represents anoptionally substituted arylene, heteroarylene or cyclohexandiyl; D is anoptionally substituted alkyl, cycloalkyl, alkoxy, alkoxycarbonyl oracyloxy; X¹ and Z¹ each independently represents a hydrogen atom,halogen atom, hydroxyl, optionally substituted amino, arylthio orheteroarylthio, and Y¹ represents a hydrogen atom, halogen atom,hydroxyl, optionally substituted amino or arylthio provided X¹, Y¹ andZ¹ are not all hydrogen.
 2. The liquid crystal composition of claim 1,wherein the anthraquinone compound is represented by formula (3) below:

where S is a sulfur atom; A, B and C each independently represents anoptionally substituted arylene, heteroarylene or cyclohexandiyl; D is anoptionally substituted alkyl, cycloalkyl, alkoxy, alkoxycarbonyl oracyloxy; and Z² represents an optionally substituted arylthio orheteroarylthio.
 3. The liquid crystal composition of claim 1, whereinthe anthraquinone compound is represented by formula (4) below:

where S is a sulfur atom; A, B and C each independently represents anoptionally substituted arylene, heteroarylene or cyclohexandiyl; D is anoptionally substituted alkyl, cycloalkyl, alkoxy, alkoxycarbonyl oracyloxy; and Z³ represents an optionally substituted arylthio.
 4. Theliquid crystal composition of claim 1, wherein the anthraquinonecompound is represented by formula (5) below:

where S is a sulfur atom; A, B and C each independently represents anoptionally substituted arylene, heteroarylene or cyclohexandiyl; D is anoptionally substituted alkyl, cycloalkyl, alkoxy, atkoxycarbonyl oracyloxy; Z⁴ represents an optionally substituted arylthio orheteroarylthio; and Z⁵ represents an optionally substituted arylthio. 5.The liquid crystal composition of claim 1, wherein the anthraquinonecompound is represented by formula (6) below:

where S is a sulfur atom; A, B and C each independently represents anoptionally substituted arylene, heteroarylene or cyclohexandiyl; D is anoptionally substituted alkyl, cycloalkyl, alkoxy, alkoxycarbonyl oracyloxy; Z⁶ and Z⁷ each independently represents an optionallysubstituted arylthio.
 6. The liquid crystal composition of claim 1,wherein at least one of Z¹, X¹ and Y¹ represents an alkylamino.
 7. Theliquid crystal composition of claim 1 wherein the liquid crystalcompound is at least one fluorine-containing liquid crystal.
 8. Theliquid crystal composition of claim 1, wherein the content of thecompound represented by the formula (1) is 0.1 to 15 wt % based on thetotal weight of the liquid crystal composition.
 9. A liquid crystal cellcomprising a liquid crystal layer containing a liquid crystalcomposition of claim
 1. 10. The liquid crystal cell of claim 9, which isa guest-host mode liquid crystal cell.
 11. A display device comprising aliquid crystal cell comprising a liquid crystal layer containing aliquid crystal composition of claim
 1. 12. The display device of claim11, wherein the liquid crystal cell is a guest-host mode liquid crystalcell.
 13. A compound represented by formula (1-a) below:

where S is a sulfur atom; A, B and C each independently represents anarylene, heteroarylene or cyclohexandiyl, wherein said arylene,heteroarylene or cyclohexandiyl may have substituent(s); D represents anoptionally substituted alkyl, cycloalkyl, alkoxy, alkoxycarbonyl oracyloxy; X^(a) and Z^(a) each independently represents a hydrogen atom,optionally substituted amino, arylthio or heteroarylthio, y^(a)represents a hydrogen atom, optionally substituted amino or arylthio;provided at least one of X^(a), y^(a) and Z^(a) represents an optionallysubstituted arylthio, wherein the -A-B-C- structure is connected througha single bond without any linking group between the rings.
 14. Thecompound of 13, wherein X^(a) and Z^(a) are hydrogen, and y^(a) is anarylthio which may have substituent(s).
 15. The compound of claim 13,wherein X^(a), y^(a), and Z^(a) each independently represents anarylthio which may have substituent(s).
 16. The compound of claim 13,wherein y^(a) and Z^(a) are each independently alkylamino or arylaminowhich may have substituent(s), and X^(a) is a hydrogen atom or anarylthio which may have substituent(s).
 17. The liquid crystalcomposition of claim 3 wherein A and B each independently represents anoptionally substituted arylene; C represents an optionally substitutedcyclohexandiyl; and D represents an optionally substituted alkyl. 18.The compound of 13, wherein A and B each independently represents anarylene which may have substituent(s); C represents an cyclohexandiylwhich may have substituent(s); and D represents an optionallysubstituted alkyl.
 19. The compound of claim 13, wherein A, B and C eachindependently represents a phenylene, naphthylene, anthrathenylene,pyridin-diyl, quinolin-diyl, isoquinolin-diyl, pyrimidylene,pyrazin-diyl, thiophenylene, furanylene, oxazolylene, thiazolylene,imidazolylene, pyrazolylene, oxadiazolylene, thiadiazolylene,triazoylenephenylene, a bivalent group of fused aromatic rings formed orby condensation thereof or (E)-cyclohexan-1,4-diyl, which may havesubstituent(s).